ABSTRACT

As people pay more attention to the aesthetics of teeth, the adhesion of brackets in the orthodontic process received a wider application in recent years. In this paper, experiments and finite element method (FEM) were combined to study the mechanical behaviour of adhesively bonded orthodontic brackets, as well as fracture performance in the adhesive layer. The tensile, shear and mode I/II fracture testing were carried out first to determine reliable parameters of the adhesive for numerical simulation. Quasi-static tensile-shear loading was applied to determine the failure strength of bracket bonded with enamel. Bi-linear cohesive element was inserted to simulate the failure process of the adhesive layer. The failure strength obtained by experiments and FEM were 8.25 MPa and 9.15 MPa, respectively, with deviation of 9.8%. The load–displacement curves obtained by simulation and experiment were in acceptable agreement. The damage propagation and stress distribution in the adhesive layer and enamel during tensile-shear loading were then analysed. The proposed FE method can be used to predict the bonding strength of brackets, and thus provide reliable reference for the force applied during clinical treatment and possible fracture mechanism during daily use of orthodontic brackets.

摘要

随着人们对牙齿美学的重视，托槽粘连在正畸过程中得到了越来越广泛的应用。本文结合实验和有限元法（FEM）研究了粘接正畸托槽的力学行为，以及粘接层的断裂性能。首先进行拉伸、剪切和模式 I/II 断裂试验，以确定用于数值模拟的粘合剂的可靠参数。应用准静态拉伸剪切载荷来确定搪瓷托槽的破坏强度。插入双线性粘性单元以模拟粘合层的破坏过程。实验和有限元法得到的破坏强度分别为8.25 MPa和9.15 MPa，偏差为9.8%。通过模拟和实验获得的载荷-位移曲线在可接受的一致性。然后分析了拉伸剪切加载过程中粘合剂层和牙釉质中的损伤传播和应力分布。所提出的有限元方法可用于预测托槽的结合强度，从而为临床治疗时所施加的力以及日常使用正畸托槽时可能发生的断裂机制提供可靠的参考。